CCG-2961 tested an intensively timed induction therapy consisting of cytarabine (AC), etoposide, thioguanine, dexamethasone, idarubicin and daunorubicin. Patients in remission after induction were randomized to a second induction course (Arm A) or a 3-drug combination of fludarabine, AC, and idarubicin (Arm B). Course 3 for patients with related donors was bone marrow transplantation (BMT); for those without donors, high dose AC/l-asparaginase. After Course 3 patients without donors were randomized to 14 infusions of Interleukin 2 (IL2) over 18 days or follow-up. CNS prophylaxis was intrathecal AC. Eligibility included all subtypes of de novo AML except acute promyelocytic leukemia and AML in patients with Down syndrome. CCG-2961 opened in Oct.1996 and closed in Dec. 2002. The DSMC suspended the study between Oct. 1999 and May 2000 while the 2961 Committee developed supportive care policies to reduce treatment-related mortality (TRM). CCG-2961 enrolled 900 de novo patients aged 3 days to 21 years, with 495 and 405 patients accruing pre-and post suspension respectively. Remission induction rate is 88.5%. With median follow-up of 3.6 years (range: 0 – 8.1 years), event-free survival (EFS) at 3 years is 44±3% and survival (OS) 57±3%. Disease-free survival (DFS) following Course 2 Arms A and B are not different, although relapse is significantly higher in Arm A (7.3% .vs. 3.1% P=0.018) and TRM more common in Arm B (7.9% vs.4.2% P=0.059), despite 7 less days of neutropenia in Arm B (P<0.001). DFS is 65±9% for patients with a donor versus 50±5% for patients without a donor (P=0.005); respective OS, 74±8% and 66±5% (P=0.221). However, among 98 patients in CR1 with t(8;21) or inv(16) cytogenetics, outcomes in those without and with a donor were no different: DFS (61±12% vs. 72±18%, P = 0.49) and OS (78±10% vs. 77±17%, l P= 0.85). DFS with and without IL2 is 55±9% and 60±8%(P=0.606). Outcomes improved progressively over time. EFS pre- and post-suspension are 41±4% and 47±5%(P=0.038); OS, 52±5% and 63±5%(P=0.005); TRM is 17±3% pre- and 12±3% post-suspension (P=0.039). Factors predictive of inferior EFS are age >17 years, Afro-American and Hispanic ethnicity, body mass index <10th or >95th percentile for age, absence of related marrow donor, WBC > 50,000/mm3, karyotype with −7/7q, −5/5q- or > cytogenetic 5 abnormalities, FLT3/ITD, >15 % morphologic blasts on day 14 or >0.5% immunologically detectable blasts at the end of induction. CCG-2961 confirms the efficacy and high TRM of intensively timed therapy. Neither fludarabine nor IL2 increases DFS or OS, and availability of a donor does not improve outcomes in those with favorable cytogenetics.